add examples

examples/log_injection/README.md

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+# Log Correlation Example
+
+This is a `docker compose` setup showcases log correlation by creating two services: Datadog Agent and Kong Gateway.
+
+The Kong Gateway is configured to generate and send distributed traces to Datadog, and the [file-config](https://docs.konghq.com/hub/kong-inc/file-log/)
+plugin to generate logs that will also be sent to Datadog. The entire configuration is located in [kong.yaml](./kong.yaml).
+
+To run this example, you will need a valid Datadog API key and Docker installed.
+
+### How to run the example
+
+1. Start the services using Docker Compose with you Datadog API key:
+
+```shell
+DD_API_KEY=<KEY> docker compose up
+```
+
+2. Grant the `kong-dbless` service permission to create the log file in the shared volume:
+```
+docker compose exece kong-dbless chown -R kong /shared
+```
+
+3. Send a request to Kong to generate traffic and a trace:
+```shell
+curl http://localhost:8000/foo
+{
+  "headers": {
+    "Accept": "*/*",
+    "Host": "httpbin.org",
+    "Traceparent": "00-c9a6361300000000269a8b8c076bafcb-55eb48277a5d69e1-01",
+    "Tracestate": "dd=p:55eb48277a5d69e1;s:1;t.tid:c9a6361300000000;t.dm:-0",
+    "User-Agent": "curl/8.6.0",
+    "X-Amzn-Trace-Id": "Root=1-66587c78-12932e884e34a78e68008bc4",
+    "X-Datadog-Parent-Id": "6191121447144745441",
+    "X-Datadog-Sampling-Priority": "1",
+    "X-Datadog-Tags": "_dd.p.tid=c9a6361300000000,_dd.p.dm=-0",
+    "X-Datadog-Trace-Id": "2781689153390882763",
+    "X-Forwarded-Host": "localhost",
+    "X-Forwarded-Path": "/foo",
+    "X-Forwarded-Prefix": "/foo"
+  }
+}
+```
+
+The trace should be reported in your Datadog account:
+![](./assets/trace.png)
+
+Additionally, the log will be available, with the ability to pivot between trace and log views:
+![](./assets/log.png)
+

examples/log_injection/docker-compose.yml

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+version: "3.2"
+
+services:
+  # `agent` is the Datadog Agent to which traces are sent.
+  # `agent` needs an API key set in the environment as the
+  # `DD_API_KEY` environment variable.
+  datadog-agent:
+    image: 'datadog/agent'
+    labels:
+      com.datadoghq.ad.logs: '[{"type": "file", "source": "kong", "service": "log-correlation-example-service", "path": "/shared/log-tracing.log"}]'
+    ports:
+      - 8136:8136
+    volumes:
+      - '/var/run/docker.sock:/var/run/docker.sock:ro'
+      - '/proc/:/host/proc/:ro'
+      - '/sys/fs/cgroup/:/host/sys/fs/cgroup:ro'
+      - shared-volume:/shared:ro
+    environment:
+      - DD_SITE
+      - DD_API_KEY
+      - DD_APM_ENABLED=true
+      - DD_LOGS_ENABLED=true
+      - DD_LOG_LEVEL=ERROR
+
+  kong-dbless:
+    image: 'kong/kong-gateway:3.3.0.0'
+    user: root
+    links:
+      - datadog-agent
+    volumes:
+      - ./kong.yaml:/kong/declarative/kong.yaml
+      - ../../kong:/tmp/custom_plugins/kong
+      - shared-volume:/shared
+    environment:
+      - DD_SERVICE=log-correlation-example-service
+      - DD_AGENT_HOST=datadog-agent
+      - KONG_DATABASE=off
+      - KONG_LOG_LEVEL=info
+      - KONG_DECLARATIVE_CONFIG=/kong/declarative/kong.yaml
+      - KONG_PROXY_ACCESS_LOG=/dev/stdout
+      - KONG_ADMIN_ACCESS_LOG=/dev/stdout
+      - KONG_PROXY_ERROR_LOG=/dev/stderr
+      - KONG_ADMIN_ERROR_LOG=/dev/stderr
+      - KONG_ADMIN_LISTEN=0.0.0.0:8001
+      - KONG_ADMIN_GUI_URL=http://localhost:8002"
+      - "KONG_LUA_PACKAGE_PATH=/tmp/custom_plugins/?.lua;;"
+      - "KONG_PLUGINS=bundled,ddtrace"
+    ports:
+      - 8000:8000
+      - 8001:8001
+      - 8002:8002
+      - 8003:8003
+      - 8004:8004
+      - 8443:8443
+      - 8444:8444
+      - 8445:8445
+
+volumes:
+  shared-volume:

examples/log_injection/kong.yaml

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+_format_version: "3.0"
+_transform: true
+
+services:
+- name: service-a
+  url: http://httpbin.org/headers
+  plugins:
+    - name: ddtrace
+    - name: file-log
+      config:
+        path: /shared/log-tracing.log
+        custom_fields_by_lua:
+          dd.trace_id: return kong.ctx.shared.datadog_sdk_trace_id
+          dd.span_id: return kong.ctx.shared.datadog_sdk_span_id
+  routes:
+  - name: my-route-a
+    paths:
+    - /foo